RGS tank cap leakage

[a101960]

Can I ask all you people that have RGS’s or RGS reps what your experiences (if any) are of fuel spillage from the petrol tank when the tank is full. The petrol fuel cap on mine has always proved to be a bit incontinent when the tank is completely full, especially if I ride over a less than 100% smooth road surface. This afternoon I dismantled the filler cap an found that the rubber gasket was in a very poor condition so clearly that has not helped the situation. Earlier in the week I purchased a replacement gasket made from 1/8” thick cork which I have now fitted. I have been unable to test how effective this is because it has been pouring down with rain, and I don’t do getting wet if I can possibly avoid it. I have also fitted a flexible pipe to the tank breather and routed that so that any spillage is hopefully contained from that source. Has anyone else done this? I am hoping that I will not have to be continually wiping the tank down in future. I just wondered if this was a common problem.
John

[bsa-bill]

Hi John
had the self same problem, if you have the cap with what looks like a big wing nut on top.
Took it off, hacksawed the hinge off ( slowly even on the empty tank) and fitted a  flip type with sort of automatic latch
like this one http://www.classicbikeshop.co.uk/monza-flip-up-style-cap-2-1-2-inch.html

can't recall the size but did not need the brass adapter I bought at the same time, the rim of the cap was a good fit and I tight, I forced it on and glued it with something as well
intended to drill and pin it through the rim as well but not got that far yet.
Sorry maybe a bit vague, but the original cap rubber just seemed to melt into a useless shape , perhaps the old Ethanol thing

[chaterlea25]

Hi All,
I have found that a lot of the pattern GS/RGS caps are crap?
The "legs" that engage with the tank are soft as putty and do not grip the tank neck
The last one I sorted using the legs from an old (rusty) cap

HTH
John

[sprint]

I have the same problem with my pattern RGS tank cap. If you fill it right up it will leak whilst riding or moving the bike around. Have to only fill to about half way up the saddle and even then it can leak at times. Not sure if the original ones are any better?

[a101960]

Since my last post I have had a chance to try the bike out. The cork gasket that I fitted has been a great improvement although not a complete cure, and the reason for this is that the diameter of the gasket is slightly undersize. This is the reason that the exercise has not been a complete success. The gasket tends to displace itself to one side as you swing the cap to the closed position, and because the neck rim is so narrow when this happens the pressure on the gasket is not evenly distributed.  I intend to go to Hobby Craft and see if I can find a piece of cork from which I can fabricate a gasket that is a snug fit in the cap to prevent it from moving out of position. The 1/8" thickness seems to be about right. I do not think that cork will be a permanent long term solution though, because eventually the petrol will degrade it. I think that a PTFE gasket will probably be the best solution to this problem. I have also fitted a piece of tube to the tank breather pipe and this has worked well in catching spillage from this source. I did notice that fuel also escapes from the small hole in the top of the cap. Not much that can be done about that, but the amount that gets out from this source is minimal. So, there are three separate sources for the fuel to escape. Based on my experience with the cork gasket that I fitted, and the fitting of the breather pipe tube I am now pretty sure that the spillage problem can be resolved.
John